JPH07287132A - Drawing method for plastic optical fiber - Google Patents

Abstract

PURPOSE:To provide a drawing method capable of maintaining mechanical strength when a fiber is formed and assuring long-term reliability as a plastic optical fiber. CONSTITUTION:This drawing method of the plastic optical fiber 5 comprises heating and melting a plastic preform 3 consisting of a core 2 and clad 1 having prescribed refractive index distributions and spinning both to a prescribed outside diameter. The optical fiber 5 spun to the prescribed yarn is coated with a UV curing type resin having a Young's modulus >=10kg/mm<2> as a protective film 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drawing a plastic optical fiber. More specifically, the present invention relates to a method for drawing a plastic optical fiber that can maintain the mechanical strength when formed into a fiber and guarantee long-term reliability.

[0002]

2. Description of the Related Art An optical fiber whose core and clad are made of plastic is used, for example, as a short-distance optical transmission line between electronic devices for transmitting and receiving optical communication, in which transmission loss is not a problem, compared to glass fiber. It is widely used because it is easy and low-priced, and is especially important in the concept of next-generation communication networks such as LAN and ISDN.

As a plastic optical fiber, a step index (SI) type fiber having a stepwise refractive index distribution as shown in FIG. 3 has been put into practical use, but this fiber has a small transmission capacity and is used for communication. Not suitable. In order to use it for communication, it is necessary to use a graded index (GI) type fiber having a large transmission capacity and having a continuous refractive index distribution as shown in FIG.

Conventionally, as a method for producing a plastic optical fiber, for example, as disclosed in Japanese Patent Laid-Open No. 4-124602, a core material is spun to a predetermined outer diameter and a clad material is coated thereon. However, in order to manufacture a GI type plastic optical fiber by this method, coating must be performed in many steps, and the process is complicated.

[0005]

Therefore, if a plastic preform consisting of a core and a clad having a GI type refractive index distribution is synthesized, heated in a drawing furnace, melted and spun to form a fiber. By reducing the coating process, it becomes possible to fabricate various fibers having different outer diameters.

However, the method of inserting the GI preform into the drawing furnace for drawing has a problem that the strength of the fiber is small.

The present invention has been made in view of the above prior art, and it is an object of the present invention to provide a drawing method capable of maintaining the mechanical strength when formed into a fiber and ensuring the long-term reliability of a plastic optical fiber. To aim.

[0008]

The structure of the present invention which achieves such an object is a plastic optical fiber in which a plastic preform comprising a core and a clad having a predetermined refractive index is heated and melted and spun to a predetermined outer diameter. A fiber drawing method is characterized in that a fiber spun to a predetermined outer diameter is coated with an ultraviolet curable resin having a Young's modulus of 10 kg / mm ² or more as a protective film. In particular, the outer diameter of the fiber is preferably 1000 μm or less, and the predetermined refractive index distribution can be a graded index type which is a continuous refractive index distribution. , Polymethylmethacrylate can be used.

[0009]

As shown in FIG. 1, the optical fiber preform 3
Is inserted into a drawing furnace 4, heated and melted, spun into a plastic optical fiber 5 having a predetermined outer diameter, further passed through an ultraviolet curing furnace 7 while being measured by an outer diameter monitor 6, and wound. By winding with the device 8, the plastic optical fiber 5 is manufactured. Here, when the optical fiber preform 3 is stretched in the lengthwise direction in the drawing furnace, the molecules of the plastic, which is a polymer, are oriented in the lengthwise direction. Since it has a random structure, it has a drawback that the tensile strength becomes weak.

Particularly, when the outer diameter of the optical fiber is 1000 μm or more, the strength is not reduced even if the orientation of the molecules is small, but when the diameter is 1000 μm or less, the strength is particularly remarkable. As described above, if the strength of the optical fiber is lowered, there is a possibility that long-term reliability when the optical fiber is laid cannot be guaranteed.

Therefore, in the present invention, as shown in FIG.
By coating the outside of the core 2 and the clad 1 of the optical fiber 5 having a predetermined refractive index distribution with a plastic layer 9 having a Young's modulus of 10 kg / mm ² or more as a protective film,
The mechanical strength is improved and the lateral pressure characteristics are also improved. The Young's modulus of the plastic layer 9 is 10 kg / m
If it is less than m ² , the strength of the plastic coating is weak and the mechanical strength of the overcoated plastic optical fiber cannot be sufficiently increased.

As the plastic layer 9 used here, in view of the heat resistance of the fiber, it is desirable to use an ultraviolet curable resin instead of a thermosetting resin. Also,
The optical fiber preform 3 has a GI type refractive index distribution shown in FIG. 4, is made of polymethylmethacrylate (PMMA) having excellent optical transparency as the cladding 1, and is made of a compound having a high refractive index for the core 2. However, the outer diameter and the length of the high refractive index compound added to the core 2 and the preform 3 should not be limited.

[0013]

EXAMPLES Specific examples of the present invention will be described below in comparison with comparative examples.

Example 1 A GI type refractive index distribution was provided.
Prepare a plastic optical fiber preform and use it for the furnace core.
Preform the drawing furnace with the temperature inside the tube set to 240 ° C.
Insert and set the outer diameter center value to 650 μm, and draw at a linear velocity of 2 m / min.
The line was drawn. Young's modulus 10kg / mm at this time ²UV hard
-Type urethane acrylate overcoat to reduce outer diameter
It was set to 800 μm. Tensile strength of manufactured fiber
Was measured to be 2.3 kg / mm²Met. This phi
When the bar was wrapped around a mandrel with a diameter of 10 mm,
Time was 10 days.

Example 2 A GI type refractive index distribution was provided.
Prepare a plastic optical fiber preform and use it for the furnace core.
Preform the wire drawing furnace with the temperature inside the tube set to 230 ° C.
Insert and set the outer diameter center value to 650 μm, and draw at a linear velocity of 2 m / min.
The line was drawn. Young's modulus at this time is 15 kg / mm ²UV hard
The outer diameter by overcoating a modified epoxy acrylate
750 μm. Tensile strength of manufactured fiber
Was measured to be 2.4 kg / mm²Met. This phi
When the bar was wrapped around a mandrel with a diameter of 10 mm,
Time was 12 days.

[Example 3] A GI type refractive index distribution was provided.
Prepare a plastic optical fiber preform and use it for the furnace core.
Preform the drawing furnace with the temperature inside the tube set to 250 ° C.
Insert and set the outer diameter center value to 650 μm, and draw at a linear velocity of 2 m / min.
The line was drawn. Young's modulus at this time is 20 kg / mm ²UV hard
Oxygenated Silicon Acrylate
It was set to 900 μm. Tensile strength of manufactured fiber
Was measured to be 2.0 kg / mm²Met. This phi
When the bar was wrapped around a mandrel with a diameter of 10 mm,
Time was 8 days.

[Comparative Example 1] A plastic optical fiber preform having a GI type refractive index distribution was prepared, and the preform was inserted into a drawing furnace set at a furnace core tube temperature of 240 ° C. The value was set to 650 μm, and drawing was performed at a linear velocity of 2 m / min. The tensile strength of the fiber produced at this time was measured and found to be 1.3 kg / mm ² . When this fiber was wound around a mandrel having a diameter of 10 mm, the time until breakage was 10 hours.

[Comparative Example 2] A plastic optical fiber preform having a GI type refractive index distribution was prepared, and the preform was inserted into a drawing furnace set to a furnace core tube temperature of 240 ° C. The value was set to 650 μm, and drawing was performed at a linear velocity of 2 m / min. At this time, the outer diameter was set to 8 by overcoating with UV curable urethane acrylate with Young's modulus of 8 kg / mm ^2.
It was set to 00 μm. The tensile strength of the produced fiber was measured and found to be 1.3 kg / mm ² . When this fiber was wound around a mandrel having a diameter of 10 mm, the time until breakage was 10 hours.

[Comparative Example 3] A plastic optical fiber preform having a GI type refractive index distribution was prepared, and the preform was inserted into a drawing furnace whose temperature in the furnace core tube was set to 240 ° C. The value was set to 650 μm, and drawing was performed at a linear velocity of 2 m / min. At this time, the outer diameter was adjusted to 8 by overcoating with UV curable epoxy acrylate with Young's modulus of 6 kg / mm ^2.
It was set to 00 μm. The tensile strength of the produced fiber was measured and found to be 1.2 kg / mm ² . When this fiber was wound around a mandrel having a diameter of 10 mm, the time until breakage was 12 hours.

[Comparative Example 4] A plastic optical fiber preform having a GI type refractive index distribution was prepared, and the preform was inserted into a drawing furnace in which the temperature in the furnace core tube was set to 260 ° C, and the center of the outer diameter was set. The value was set to 650 μm, and drawing was performed at a linear velocity of 2 m / min. At this time, a thermosetting urethane acrylate resin was overcoated to have an outer diameter of 800 μm. The produced fiber had a poor appearance due to heat shrinkage, and the strength could not be measured.

[Comparative Example 5] A plastic optical fiber preform having a GI type refractive index distribution was prepared, and the preform was inserted into a drawing furnace in which the temperature in the furnace core tube was set to 260 ° C, and the center of the outer diameter was set. A linear velocity of 1.5 m / mi with a value of 650 μm
The line was drawn with n. At this time, a thermosetting epoxy acrylate resin was overcoated to have an outer diameter of 800 μm. The produced fiber had a poor appearance due to thermal contraction as in Comparative Example 4, and the strength could not be measured.

[Comparative Example 6] A plastic optical fiber preform having a GI type refractive index distribution was prepared, and the preform was inserted into a drawing furnace in which the temperature inside the furnace core tube was set to 275 ° C, and the center of the outer diameter was set. Linear velocity of 2 m / min with a value of 1100 μm
I drew the line. The tensile strength of the produced fiber was measured and found to be 2.2 kg / mm ² . When this fiber was wound around a mandrel having a diameter of 10 mm, the time until breakage was 10 days, and no decrease in strength was observed.

[0023]

As described above in detail with reference to the embodiments, the present invention is a method for drawing a plastic optical fiber. In the method of drawing a plastic optical fiber, an ultraviolet curable resin having a Young's modulus of 10 kg / mm ² or more is used as a protective film on the fiber. As a result of overcoating, the mechanical strength of the fiber can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method for drawing a plastic optical fiber according to the present invention.

FIG. 2 is a cross-sectional view of a plastic optical fiber preform according to the present invention.

FIG. 3 is a refractive index profile of an SI type fiber.

FIG. 4 is a refractive index profile of a GI type fiber.

[Explanation of symbols]

 1 clad 2 core 3 plastic optical fiber preform 4 heating furnace 5 plastic optical fiber 6 outer diameter monitor 7 ultraviolet curing furnace 8 winding device 9 plastic layer (protective film)

Claims (4)

[Claims] 1. A method for drawing a plastic optical fiber, wherein a plastic preform having a core and a clad having a predetermined refractive index distribution is heated and melted and spun to a predetermined outer diameter, which is spun to a predetermined outer diameter. A method for drawing a plastic optical fiber, characterized in that the optical fiber is coated with an ultraviolet curable resin having a Young's modulus of 10 kg / mm ² or more as a protective film. 2. The method for drawing a plastic optical fiber according to claim 1, wherein the outer diameter of the optical fiber is 1000 μm or less. 3. The method for drawing a plastic optical fiber according to claim 1, wherein the predetermined refractive index distribution is a graded index type having a continuous refractive index distribution. 4. The method for drawing a plastic optical fiber according to claim 1, wherein polymethyl methacrylate is used for the clad.